The invention relates to arc interrupters.
An electric switch has been proposed, for example in United Kingdom patent application No. 79 39949 (Publication No. 2044538 A), in which in an arc interrupter used therein an arc drawn between separating contacts is transferred from a fixed contact to an annular arcing electrode which is coaxial with an arc-driving coil through which the arc current flows. The resulting magnetic field drives the arc around the electrode and ultimately the arc is extinguished.
The arc roots on the movable contact which, in its fully open break position, should ideally be exactly centrally positioned with respect to the electrode. However, the behaviour of the arc after it has been transferred is very sensitive to the relative positioning of the contact and the electrode. Any eccentricity in the positioning of the contact can cause erratic arc movement, inefficient extinguishment of the arc and burning of the surfaces at which the arc roots.
A theoretical discussion relating to the rotation of arcs to assist in the extinguishment thereof is given in a paper by Fujiwara, K., Ono, S.I., entitled "Rotating Arc Driven by Magnetic Flux in SF.sub.6 Gas", 2nd International Symposium on Switching Arc Materials, Part II (Post conference materials), Lodz Poland, Sept. 25-27, 1973, (published Lodz, Poland: Tech. Univ. Lodz 1975), pages 62-67.